Contact sensitivity induced in mice by methylene bisphenyl diisocyanate

Isocyanates may contribute to allergic contact dermatitis from diabetes devices and wound dressings

BACKGROUND

Isocyanates are well-known occupational allergens, but can also be present in medical devices.

OBJECTIVES

To highlight that contact sensitization to isocyanates might contribute to allergic contact dermatitis (ACD) from polyurethane (PU)-containing diabetes devices and wound dressings.

PATIENTS AND METHODS

Nineteen patients with suspected allergic contact dermatitis (ACD) from diabetes devices and/or wound dressings were patch tested to an isocyanate series. Four wound dressings, 6 diabetes devices and 4 monomeric isocyanate patch test preparations were analysed with gas chromatography - mass spectrometry (GC/MS).

RESULTS

Eight patients reacted to isocyanates and corresponding amines: 3 to isophorone diisocyanate (IPDI), 4 to 4,4'-diaminodiphenylmethane (MDA), 4 to 2,4-toluene diisocyanate (TDI) and 1 to polymeric methylene diphenyl diisocyanate (PMDI). Three of 4 wound dressings contained isocyanates (MDI, TDI and/or IPDI), whereas 5 of 6 diabetes devices contained 4,4'-methylene diphenyl diisocyanate (MDI), and one of them also IPDI. None of the medical devices contained 1,6-hexamethylene diisocyanate (HDI). Contrary to IPDI, and especially MDI, only the concentration of the TDI patch test preparation corresponded approximately (80%) to its label.

CONCLUSION

Patch tests with isocyanates may be worth-while in patients with suspected ACD from PU-containing medical devices. Besides MDA, and PMDI, also TDI might potentially be a marker for MDI-sensitization. This article is protected by copyright. All rights reserved.

Sensitizing Capacities and Cross-Reactivity Patterns of Some Diisocyanates and Amines Using the Guinea-Pig Maximization Test. Can p-phenylenediamine be Used as a Marker for Diisocyanate Contact Allergy?

Background:

Isocyanates are mainly considered respiratory allergens but can also cause contact allergy. Diphenylmethane-4,4′-diamine (4,4′-MDA) has been considered a marker for diphenylmethane-4,4′-diisocyanate (4,4′-MDI) contact allergy. Furthermore, overrepresentation of positive patch-test reactions top-phenylenediamine (PPD) in 4,4′-MDA positive patients have been reported.

Objectives:

To investigate the sensitizing capacities of toluene-2,4-diisocyanate (2,4-TDI) and PPD and the cross-reactivity of 4,4′-MDA, 2,4-TDI, dicyclohexylmethane-4,4′-diamine (4,4′-DMDA), dicyclohexylmethane-4,4′-diisocyanate (4,4′-DMDI), 4,4′-MDI and PPD.

Methods:

The Guinea Pig Maximization Test (GPMT) was used.

Results:

PPD was shown to be a strong sensitizer (p<0.001). Animals sensitized to PPD showed cross-reactivity to 4,4′-MDA (p<0.001). Animals sensitized to 4,4′-MDA did not show cross-reactivity to PPD. 8 animals sensitized to 2,4-TDI were sacrificed due to toxic reactions at the induction site and could thus not be fully evaluated.

Conclusion:

PPD was shown to be a strong sensitizer. However, it cannot be used as a marker for isocyanate contact allergy. On the other hand, positive reactions to 4,4′-MDA could indicate a PPD allergy. The intradermal induction concentration of 2,4-TDI (0.70% w/v) can induce strong local toxic reactions in guinea-pigs and should be lowered.

Dipeptidyl peptidase IV (DPP4) deficiency increases Th1-driven allergic contact dermatitis

BACKGROUND

CD26 or dipeptidyl peptidase IV (DPP4) is known to be involved in several immunological processes and has recently been reported to play a crucial role in the allergic responses of the lungs.

OBJECTIVES

To explore the impact of DPP4 on the allergic response of the skin.

METHODS

Skin biopsies from patients suffering from atopic dermatitis (AD) and healthy controls were investigated for the expression of CD26/DPP4. Furthermore, the functional impact of CD26 was investigated in two models of contact hypersensitivity using CD26/DPP4-deficient and wild-type rats. Dinitrochlorobenzene (DNCB) was used to induce a T helper type 1 (Th1)-dominated inflammation and toluene-2,3-diisocyanate for a Th2-pronounced inflammation. The inflammatory responses were determined by histological quantification, flow cytometry [fluorescence-activated cell sorting (FACS)], and an enzyme-linked immunosorbant assay (ELISA).

RESULTS

CD26/DPP4-expression was up-regulated in the lesional skin biopsies of patients compared with healthy controls as well as in both models of contact hypersensitivity. However, in the more Th2-driven model, a reduced inflammatory skin response was found in CD26/DPP4-deficient rats, analogous to the effects observed recently in a rat model of asthma. In partial contrast, there was an aggravation of local skin inflammation in CD26/DPP4-deficient rats under conditions of Th1-like skin inflammation.

CONCLUSION AND CLINICAL RELEVANCE

The up-regulation of CD26 in atopic dermatitis represents a new finding, which has also been seen in other inflammatory skin diseases. However, tissue expression of CD26/DPP4 in immunological skin response can either be beneficial or aggravating, depending on a possible Th1/Th2 shift. This might have consequences for humans suffering from diabetes mellitus treated by DPP4 inhibitors, who have eczematous skin diseases as a co-morbidity.

Hand/face/neck localized pattern: sticky problems--resins

Plastic resin systems have an increasingly diverse array of applications but also induce health hazards, the most common of which are allergic and irritant contact dermatitis. Contact urticaria, pigmentary changes, and photoallergic contact dermatitis may occasionally occur. Other health effects, especially respiratory and neurologic signs and symptoms, have also been reported. These resin systems include epoxies, the most frequent synthetic resin systems to cause contact dermatitis, (meth)acrylics, polyurethanes, phenol-formaldehydes, polyesters, amino resins (melamine-formaldehydes, urea-formaldehydes), polyvinyls, polystyrenes, polyolefins, polyamides and polycarbonates. Contact dermatitis usually occurs as a result of exposure to the monomers and additives in the occupational setting, although reports from consumers, using the raw materials or end products periodically surface. Resin- and additive-induced direct contact dermatitis usually presents on the hands, fingers, and forearms, while facial, eyelid, and neck involvement may occur through indirect contact, eg, via the hands, or from airborne exposure. Patch testing with commercially available materials, and in some cases the patient's own resins, is important for diagnosis. Industrial hygiene prevention techniques are essential to reduce contact dermatitis when handling these resin systems.

Cytokine mRNA profiles for isocyanates with known and unknown potential to induce respiratory sensitization

Isocyanates are low-molecular-weight chemicals implicated in allergic asthmatic-type reactions. Identification of chemicals likely to cause asthma is difficult due to the lack of a validated test method. One hypothesis is that differential cytokine induction (Th1 versus Th2 profiles) in the draining lymph node following dermal application can be used to identify asthmagens and distinguish them from contact allergens. In this study, we compared the cytokine mRNA profiles of six chemicals: toluene diisocyanate (TDI), diphenylmethane-4,4'-diisocyanate (MDI), dicyclohexylmethane-4,4'-diisocyanate (HMDI), isophorone diisocyanate (IPDI), p-tolyl(mono)isocyanate (TMI), and meta-tetramethylene xylene diisocyanate (TMXDI). Whereas TDI and MDI are well-known respiratory sensitizers, documentation for HMDI, IPDI, TMI, and TMXDI is limited, but suggests that HMDI and IPDI may have respiratory sensitization potential in humans and TMI and TMXDI do not. Following dermal exposure of BALB/c mice, all six isocyanates induced cytokines characteristic of a Th2 response. Although LLNAs suggested that the doses chosen for the RPA were immunologically equivalent, the isocyanates tested differentiated into two groups, high responders and low responders. However, two of the low responders (TMI and TMXDI) were further tested and induced higher levels of Th2 cytokine message than dinitrochlorobenzene (not an asthmagen). Further study of these chemicals is needed to determine whether the Th2 cytokine responses observed for these low responders is predictive of asthmagenic potential or represents an insufficient signal.

Evaluation of self-reported skin problems among workers exposed to toluene diisocyanate (TDI) at a foam manufacturing facility

Toluene diisocyanate, or TDI (CAS 584-84-9) is a well-known asthmagen and respiratory irritant. TDI is also known for its ability to irritate the skin and mucous membranes. To further investigate the dermal effects of TDI, NIOSH investigators conducted a cross-sectional study at a flexible foam manufacturing plant. A total of 114 workers participated in the study. Participants completed a medical questionnaire, provided blood for antibody testing to TDI and other allergens, and a subset of participants reporting skin symptoms underwent skin patch testing to a standard diisocyanate panel. Production line workers were more than twice as likely to report skin problems as those working in nonproduction areas (PRR = 2.66; 95% CI = 1.14-16.32; P = 0.02). Age, gender and duration of employment at the plant were comparable among participants working in production and nonproduction areas. Of the 100 participants who provided blood samples for antibody testing, specific IgG antibody to TDI was detected in two individuals, and none of the samples demonstrated specific IgE antibody to TDI. Of the 26 workers who underwent skin patch testing, none developed reactions to the diisocyanate allergens. These results suggest that the skin symptoms among study participants represent an irritant rather than an immunologic reaction to TDI, or to an unidentified allergen present in the foam.

Occupational dermatitis from exposure to polyurethane chemicals

In addition to asthma, contact dermatitis may also develop from occupational contact with polyurethane (PU) chemicals. 6 cases of allergic contact dermatitis from exposure to PU chemicals were diagnosed in 1974-1990. The present paper summarizes the results and gives detailed descriptions of 3 such patients. 3 patients were allergic to 5 different diisocyanates (DICs), including 4,4'-diphenylmethane DIC (MDI), toluene DIC (TDI), 1,6-hexamethylene DIC (HID), and furthermore to diaminodiphenylmethane (MDA). 3 patients were sensitized by exposure to MDI. 2 of these reacted to MDI and MDA, and 1 to TDI in addition. 1 of the 3 patients reacted only to MDA, possibly formed by hydrolysis of MDI. Primary sensitization to MDA and cross-allergy to MDI could explain the reactions of the patients exposed to MDI, but separate sensitization may also be possible. Patch tests with fresh petrolatum (pet.) mixtures were first made and a 2% concentration was recommended for MDI and TDI. In order to determine the stability of DIC test substances, the last 2 patients were tested with old test substances. Tests with MDI 1.5% pet. and TDI 1.5% pet., 5.5 months and 15.5 months old, were positive. The results suggest that, when allergy to PU chemicals is suspected, patch tests should include, in addition to MDA, at least MDI and TDI 1.5-2% pet. They also suggest that test substances can be used for over a year, and that allergy to MDA may point to MDI exposure contained in PU chemicals.

Identification of contact allergens using the murine local lymph node assay: comparisons with the Buehler occluded patch test in guinea pigs

A murine local lymph node assay has been developed for the identification of contact sensitizing chemicals. In the present study, the performance of the local lymph node assay has been evaluated with twenty-four coded chemicals of previously unknown skin sensitizing potential and the results compared with predictions made from concurrent occluded patch tests (Buehler tests) in guinea pigs. The data presented demonstrate that the local lymph node assay successfully identified those chemicals that were classified as moderate or strong skin sensitizers in the Buehler test. In the present series of experiments, chemicals predicted to be mild sensitizers in the Buehler test were classified as 'not strong sensitizers' in the local lymph node assay. In the majority of instances, the Buehler test and local lymph node assay were in agreement with regard to the identification of non-sensitizing chemicals. However, two chemicals that were classified as non-sensitizers in the guinea pig test exhibited positive responses in the local lymph node assay and were predicted to be sensitizers. Some coloured chemicals resulted in obscured Buehler readings and, here, assessment was based upon histological examination of the challenge site. These compounds were examined also in the local lymph node assay and similar predictions of sensitizing potential were made. Taken together, the data reveal close, but not absolute, concordance between the local lymph node assay and the Buehler test. The relative merits of these predictive test methods are discussed.

Aspects of the immune response to contact allergens: opportunities for the development and modification of predictive test methods

A variety of guinea-pig tests are currently employed to assess the skin-sensitizing potential of chemicals. Although some such tests, in particular the guinea-pig maximization test and the occluded patch test of Buehler, have become well established, widely applied and are of proven value in the safety evaluation of chemicals, they have certain limitations. It is the purpose of this review to examine various aspects of the immune response to contact allergens and the way in which an understanding of the molecular and cellular events that characterize the induction and elicitation of contact sensitivity may be applied to the development and modification of predictive test methods. Attention is focused on the role of dendritic cell migration and T lymphocyte activation during the induction phase of skin allergy and the association of acute-phase proteins and vasoactive amines with the elicitation reaction.